incharlest

My 2000 es300 seems to hesitate or stumble when giving the car gas after a complete stop. This seems to ONLY happen though once the car is at normal operating temperature. Also, it only happens when the car is in drive. I'm leaning towards one or more fuel injectors being bad. I bought a $200 scan tool it indicates as much as a -20 short term fuel trim. Am I on the right track? Any thoughts or recommendations would gladly be appreciated.
Thanks

SC400slide

iTrader: (11)

I'm no ES expert, but it might be dirty fuel and/or fuel filter. If not both of those, I'd get into the injectors. Reset the ECU before everything, just to see if the probs will leave

incharlest

Thanks for your input. I have run 3 or 4 tanks of gas through the car since the problem started. Also, when I first noticed the problem I went ahead and changed the fuel filter. Injectors it is. Anyone else have any thoughts?

SC400slide

iTrader: (11)

Very informative thread:
https://www.clublexus.com/forums/es3...elerating.html

incharlest

Thank you sir.

hzt30

Negative fuel trim means that the engine is running rich and the computer is taking fuel away. What does short and long term fuel trims look like at idle and at 3000 rpms? Are both banks showing negative numbers? Are the oxygen sensors responding? Does the coolant temperature sensor match the actual temperature?

incharlest

I was unable to check the car yesterday but I looked at my stored data. I do have info that might help though. First...O2S12 was usually about .70 although it is possible it went as low as .10 at 1000-14000 rpm. The other two O2 sensors are always in the 3.2 range. Second.... both fuel banks ran from -22 to 22. If one was in the negative the other would be positive. Really was no rhyme or reason. Normally this happen in the 1500 rpm range.
I'll probably be able to check your specific suggestions tomorrow or possibly today but thought I would post while fresh in my mind.
One last thought...just wanted to reiterate that the car runs perfect for about 5 minutes until it gets up to normal operating temperature

hzt30

The 3.2 range would indicate that these are A/F ratio sensors and not oxygen sensors. The only way to test these is with a scan tool. You could introduce propane in the intake and see if the sensors react. They do not switch like regular oxygen sensors do (.1 to .9 volts). They hover around the 3 volt range.

Sounds like all is OK until engine goes into closed loop mode. This is when the ECU looks at the sensors to control the engine. Again, check your coolant temperature sensor.